(1) When I click the Sign up button inside the Active Social's Login extension module, it will bring me to the Social Members > Social Profile >, but not the expect Sign up screen
If you are already logged in that is what will happen. Make sure your settings in DotNetNuke under Portal Settings are setup according to the details we provided in guide. The user profile page needs to be set up to point to the sign up page.
(2) If I click the Sign up menu item on the top bar directly, it will show me the Sign up screen. But when I fill the fields of the first screen and click the Next button, it will create the user account but will then bring me to the home page but not the expect next screen to finish the registration.
This usually means your permissions are not set properly on the page or that you didn't setup the settings properly based upon the guide.
(3) If I click the Sign up menu item on the top bar directly, it will show me the Sign up screen. But when I click the Next button directly without filling any fields, it will bring me to the home page but not the expect validation error messages.
That is the intended behavior to prevent issues with spam bots.